1. Field of the Invention
The invention concerns a novel method of mounting a lithoplate to the plate cylinder of a web press, many of which have plate cylinders with a reel bar lockup design, as do those manufactured by Harris Graphics, American Type Founders, Geo. Hantscho Co. Inc., and Timpsons Ltd. The invention produces a lithoplate, the crimped form of which is believed to be novel.
2. Description of the Prior Art
As illustrated in FIG. 1 of the drawing, a typical web press of the prior art has a plate cylinder 10 including a reel bar 12. Before being mounted, a metal lithoplate 14 is bent so that its lead edge fits over the leading edge or "bullnose" 16 of the plate cylinder and its trailing edge fits into a slot 18 in the reel bar 12. The reel bar is then cranked clockwise (as seen in FIG. 1) until the lithoplate fits tightly against the surface of the plate cylinder. To remove the lithoplate requires counterclockwise cranking of the reel bar. A skilled operator can remove one lithoplate and mount another in about one minute.
Most lithoplates have an aluminum base which is about 0.3 mm in thickness. To the underside of the base may be adhered a paper or plastic underpacking, the thickness of which is selected to provide the desired interference between the lithoplate and the blanket cylinder, usually about about 0.1 mm. Substantial cost reductions would be realized by using camera-direct plates having a plastic (i.e., polyester) base, but they would stretch under stresses encountered during printing on commercial web presses, and it is believed that no one has demonstrated how a stretchable lithoplate could successfully be used on the plate cylinder of a web press such as that illustrated in FIG. 1. For economy, the thickness of a plastic-base lithoplate would be less than 0.3 mm, so that a greater underpacking thickness would usually be necessary.